Exchange and transport in plants

Question 1

Where does the xylem move water in the plant?

Answer 1

from the roots to the leaves

Question 2

Where does the phloem move nutrients in the plant?

Answer 2

from leaves to rest of the plant

Question 3

What does the xylem transport?

Answer 3

water and minerals

Question 4

What does the phloem transport?

Answer 4

sucrose and amino acids

Question 5

What transport process is used in the xylem?

Answer 5

transpiration stream

Question 6

What transportation process is used in the phloem?

Answer 6

translocation

Question 7

What is the xylem made of?

Answer 7

elongated dead cells arranged end to end to form continuous tubes (vessels)

Question 8

How are xylem vessels adapted?

Answer 8

• they have no cytoplasm
• they are impermeable to water
• have tough walls containing lignin

Question 9

What is the phloem made of?

Answer 9

living cells arranged end to end

phloem vessels contain cytoplasm which goes through cells from one cell to the next

Question 10

What are the sources?

Answer 10

where substances are made

Question 11

What are the sinks?

Answer 11

where substances are used or stored

Question 12

Fill the gaps:

sucrose and amino acids travel from ______ to ____

Answer 12

source to sink

Question 13

What is transpiration?

Answer 13

the evaporation of water at the surfaces of cells in the leaves (spongy mesophyll cells), followed by loss of water vapour through the stomata

water travels up through plant

Question 14

How does the transpiration stream work?

Answer 14

it produces a tension or ‘pull’ on the water in the xylem vessels by the leaves
water molecules are cohesive (stick together) sp the water is pulled up through the plant

Question 15

What are the four functions of the transpiration stream?

Answer 15

• transporting mineral ions through the xylem
• providing water to keep cells turgid in order to support the plant
• provides water for the leaf cells for photsynthesis
• keeps the leaves cool by evaporation

Question 16

Transpiration stream

Fill the gaps :

travels from ____ –> ____ –> ____

Answer 16

root –> stem –> leaf

Question 17

What are the four factors that affect the rate of transpiration?

Answer 17

• temperature
• humidity
• wind speed
• light intensity

Question 18

What happens to the rate of transpiration when the temperature is increased?

Answer 18

evaporation and diffusion are faster at higher temperatures

Question 19

What happens to the rate of transpiration when the humidity is increased?

Answer 19

diffusion of water vapour out of the leaf slows down if the leaf is already surrounded. by moist air (diffusion = high –> low concentration)

Question 20

What happens to the rate of transpiration when the wind speed is increased?

Answer 20

moving air removes water vapour, increasing the rate of diffusion of water vapour from the leaf

Question 21

What happens to the rate of transpiration when the light intensity is increased?

Answer 21

the stomata open wider to allow more CO2 into the leaf for photosynthesis

Question 22

How are leaves adapted in hot climates?

Answer 22

their stomata open at night and close at midday - the stomata are closed when the rate of transpiration would be greatest - loose less water from evaporation

Question 23

Why are spines better than leaves in a hot climate?

Answer 23

reduces surface area for transpiration

Question 24

Why are reduced stomata better in a hot climate?

Answer 24

reduces transpiration rate

Question 25

Why is a waxy leaf cuticles better in hot climates?

Answer 25

impermeable to water which stops evaporation

Question 26

How can the rate of transpiration be investigated?

Answer 26

measuring the decrease in mass due to water loss

or

measuring the volume of water absorbed